# From multiple pair-collections to list of pairs

**URL:** <https://help.galaxyproject.org/t/from-multiple-pair-collections-to-list-of-pairs/7011>\
**Category:** Uncategorized\
**Tags:** collections\
**Created:** [November 9, 2021, 12:44pm UTC](https://help.galaxyproject.org/t/from-multiple-pair-collections-to-list-of-pairs/7011 "2021-11-09T12:44:33Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Peter\_van\_Heusden](https://sea2.discourse-cdn.com/flex020/user_avatar/help.galaxyproject.org/peter_van_heusden/32/824_2.png) [@Peter\_van\_Heusden](https://help.galaxyproject.org/u/Peter_van_Heusden)\
**Post date:** [November 9, 2021, 12:44pm UTC](https://help.galaxyproject.org/t/from-multiple-pair-collections-to-list-of-pairs/7011/1 "2021-11-09T12:44:33Z")

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Is there a way to build a list of pairs collection from multiple collections of type pair?

Thanks!  
Peter

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<div class="post-metadata">

**Author:** ![wm75](https://sea2.discourse-cdn.com/flex020/user_avatar/help.galaxyproject.org/wm75/32/56_2.png) [@wm75](https://help.galaxyproject.org/u/wm75)\
**Post date:** [November 9, 2021, 8:22pm UTC](https://help.galaxyproject.org/t/from-multiple-pair-collections-to-list-of-pairs/7011/2 "2021-11-09T20:22:35Z")

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Hmm, tricky. Guess I have only a partial solution:

1. Use **BUILD\_LIST** with all your paired collections as inputs.
2. Run **APPLY\_RULES** with this rule:

```auto
{
  "rules": [
    {
      "type": "add_column_metadata",
      "value": "identifier0"
    },
    {
      "type": "add_column_metadata",
      "value": "identifier1"
    }
  ],
  "mapping": [
    {
      "type": "paired_identifier",
      "columns": [
        0
      ]
    },
    {
      "type": "list_identifiers",
      "columns": [
        1
      ],
      "editing": false
    }
  ]
}

```

This organizes things in the way you want them, but you will have lost the names of the original paired collections and have them replaced with element indices.  
If you generate a list of the correct names, I guess you can run:  
3. **RELABEL\_FROM\_FILE** on the list:paired collection above, but I haven’t tried that.